Optical Line Terminal (OLT) devices operate as service provider endpoints in passive optical networks (PON). The OLT converts between the electrical signals that are used by equipment of a service provider and the fiber optic signals transmitted over the PON. OLT devices continuously stream frames to multiple Customer Premises Equipment units (CPEs) for processing and forwarding. The CPEs, also referred to as optical network terminals (ONTs) or optical network units (ONUs), typically function as a gateway between a service provider network and a home or small business network.
Downstream frames that are transmitted on a PON typically comprise several predefined fields and include data packets (user traffic) as well as various control structures for managing the connection between the OLT and CPE, and for coordinating the upstream transmission time division multiplexing (TDM) mechanism employed by CPE devices on the other end of that network. In the upstream direction, PON CPE devices are expected to transmit upstream frame when requested by the OLT. The upstream frames may contain data packets (user traffic), idle frames or/and various status messages as well as upstream traffic reports. In an effort to maintain PON synchronization protocol and connectivity between OLT and ONUs/ONTs, even during times of inactivity when there is no user traffic to send in either directions (downstream or upstream), the OLT typically periodically transmits operation and management (OAM) messages to the CPE devices as well as upstream bandwidth allocations for CPE devices. In response to OAM messages, the CPE devices are configured transmit acknowledgment, status, or report messages as mandated by the relevant standard. In general CPE device is expected to complete a transmission during every upstream bandwidth allocation assigned to it by the OLT, when there is no user traffic or OAM messages to send to the OLT, CPE will generate and transmit idle frames and/or messages in response to the corresponding upstream bandwidth allocation as mandated by the relevant PON protocol.
The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.